Hardware

I have spent a lot of time benchmarking Tape SAN performance with an E15k
and several Crossroads 8000 FCAL routers front-ending an L700 tape library
with SDLT320 Drives and I am seeing something very strange yet 100% reproducible.

For those of you not familiar with the Crossroads 8000, it has 2 x 1Gbps FC ports, and
8 HVD SCSI.

If I use something like:

dd if=/dev/zero of=/dev/rmt/0cbn bs=512k

I will get about 37Mbps throughput to a single drive from a SUN X6767A or X6768A
HBA port. If I send more streams from that host bus adapter to the same FC port
on the Crossroads I end up with 2 x 23Mbps streams, or 3 x 13Mbps streams.

The interesting thing is that if I send those streams from the same HBA to a different
Crossroads FC Port, I will get 2x36Mbps (1 SUN HBA port to 2 Crossroads ports)

If I send from 2 Sun HBA ports to a single Crossroads FC Port I will get 2 x 36Mbps.

It seems as if the SUN HBA's have some kind of SCSI queue depth associated with
each SCS target that is probably set too low.

SunService says they don't deal with performance issues and referred us to SunPS.

Crossroads says their 8000 router works just fine and perhaps the Sun HBA is
trying to query the SDLT320 drives for speed on the SCSI bus and is throttling
througput to match up with this.

We don't think we see issues like this with JNI, but haven't had any cards available to test
with.

Question: Has anyone bumped into this 44Mbps per FCAL router port limitation with
SUN's HBAs, and/or can they send us any documentation that provides all the parameters
that can be set in the /kernel/drv/qlc.conf file? SunService claims to not have any documentation
on that config file, and we haven't seen anything in the Sun docs anywhere.

thanks,

Brian